Polycrystalline superhard materials, such as polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (PCBN) may be used in a wide variety of tools for cutting, machining, drilling or degrading hard or abrasive materials such as rock, metal, ceramics, composites and wood-containing materials. For example, tool inserts comprising PCD material are widely used in drill bits for boring into the earth to extract oil or gas. The working life of superhard tool inserts may be limited by fracture of the superhard material, including by spalling and chipping, or by wear of the tool insert.
U.S. Pat. No. 6,258,139 discloses a polycrystalline diamond compact (PDC), in which a carbide substrate is provided having a number of recesses, within which a number of diamond core protrusions are sintered in place. The diamond core protrusions and the diamond surface region may be portions of the same diamond material or not of the same diamond material. The PDC is preferably fabricated by placing a carbide substrate, having a provided cavity, in a can assembly. Diamond crystals or grains are placed into the cavity in the carbide substrate. Additional carbide is placed in the cavity over the diamond. Next, additional diamond is placed over the finished substrate with the enclosed diamond core. High pressure and high temperature are applied to sinter of the carbide diamond regions into the PDC structure.
There is a need for a superhard construction having extended working life in high wear or high impact application, such as boring into rock.